- Scientific Name: Two species of Margarodes are involved; usually M. meridionalis Morr. is the species found attacking turfgrasses in the United States. [Phylum Arthropoda: Class Insecta: Order Homoptera: Family Margarodidae]
- Common Names: ground pearls, margarodid scales
- Climatic Zone: tropical, subtropical, southern temporate
- Geographic Distribution: Generally found attacking warm season turfgrasses from Southern California across to North Carolina.
- Damaging Stage: nymphs and adults
- Hosts: Recorded form several species of native grasses but attacks bermudagrass, centipedegrass, zoysiagrass and St. Augustinegrass. Most commonly damages bermuda and centipede.
- Damage Symptoms: Irregular patches or circles of the turf appear unthrifty and over a year or two thin out or die. Turf often turns yellowish. Damage is most common during dry spells.
- Description of Stages:
Very little is known about this group of pests and descriptions are scant. Apparently a modified gradual life cycle such as is found in some mealybugs and scales is followed.
Eggs: Light pinkish, cylindrical eggs are deposited in a white waxy sac by the females.
Nymphs: The first nymphal instar, called the crawler, is about 0.2mm long. This stage attaches to a grass root and begins to cover itself with a hard coating of yellowish to light purple wax. This is the ground pearl. The encysted nymphs range from 0.5-2.0mm in diameter.
Adults: The adult females are pinkish sac-like forms, about 1.6mm long, and have well-developed front legs and shorter second and third legs. The males are rarely seen but are tiny white to pinkish gnat-like insects.
- Life Cycle and Habits: Because these insects are essentially subterranean for most of their lives, little is known about their exact behavior. Generally it is thought that there is only one generation per year though there is good evidence that some of the cysts (pearls) may delay adult emergence for two to four years. Mature females occur in late spring during which time they emerge from their hard waxy cysts and crawl to the soil surface where they mate with the tiny winged males. These females are often bright pink or pink-purple in color. Once mated, the females dig back into the soil where they lay a cluster of 20 to 100 eggs in a mass of waxy strands. The eggs hatch into crawlers which disperse in the soil in search of grass roots. When suitable grass roots are found, the crawlers attach themselves and secrete a hard waxy coating which becomes the ground pearl stage. Crawlers that do not find grass roots often will attach to weed roots. The nymphs continue to develop inside this cyst and overwinter attached to the root.
- Control Approaches: Since these pests are protected during most of their life cycle inside the waxy cyst, no insecticides have been found which is consistently effective. Even systemic insecticides do not seem to reach the roots where these insects are feeding.
Cultural Control - Maintain Healthy Turf - Watering during drought and good fertilization have been the most effective methods used to counter the damage caused by ground pearls.